Unfortunately, some little old ladies will probably turn in their deceased hubby's guns for pennies on the dollar. They'll get $50 for a S&W .357 that would go for $500 to $700 on the market. I'll bet a lot of these cops "review" the firearms that are turned in prior to having them bulldozed. These cops get a better deal than Jay Leno got on his Duesenberg.
Now that I saw the video, I think you make a good point but they could probably have sold them privately for more money. Of course, that requires some effort. This was an easy way for them to do it.
This happened twenty, thirty years ago in Chicago. Little old lady was afraid of her deceased husband's revolver, so she turned it in to the police, who were running a "gun buy back". Turned out to be a '73 Single Action Army with the lowest serial number anyone had ever seen, one of the first made. In very good condition. Worth a jillion bazillion bucks, even back then. I don't know what happened to it, but the story, with a picture of the arm made it into the Tribune real fast. I'm sure it found a home in a collection or a museum somewhere.